Three analyses of the behavioral and neural organization of early learning are proposed. These studies continue an ongoing investigation of appetitive behavior in developing rats that has: (a) defined an emerging and experience-vulnerable response system for rooting, probing, search, and exploration; (b) uncovered a system of unilateral olfactory learning underlying one component of learning; and (c) correlated developmental changes in this unilateral learning with specific events in neural maturation. A further characterization of the development and plasticity of an appetitive response system forms specific AIM #1 of this application. Experiments are proposed to trace the development of rooting/probing/search behaviors (in both the normal and a con- trolled environment; and to explore the manner in which experience modulates, disturbs, or is integrated into this developmental system. These studies broadly assess the developmental continuity and significance for later mammalian behavior of a primitive adaptive system. Experiments of Specific AIM #2 will analyze the early neurobehavioral organization of Pavlovian conditioning using the unilateral conditioning paradigm. They will assess the conditions under which unilaterally stored memories can be transferred and study the independence of specific conditioning processes. In Specific AIM #3, the neural substrates of early learning will be studied by determining which developing pathways are critical for developmental changes in unilateral conditioning and by mapping changes in neural activity occurring with learning and memory access. Transection techniques will be used to isolate pathways end deoxyglucose autoradiography will be used to help identify neural substrates of learning (applying a recently developed composite-comparison technique that produces topographical maps of differences in neural activity between groups of brains). These projects are broadly relevant to understanding mechanisms of appetitive learning. Moreover, they may have specific applicability to understanding disorders in learning that develop from inappropriate experience or disturbances in neural maturation.